heightfield.cpp

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/*
    pbrt source code Copyright(c) 1998-2010 Matt Pharr and Greg Humphreys.

    This file is part of pbrt.

    pbrt is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.  Note that the text contents of
    the book "Physically Based Rendering" are *not* licensed under the
    GNU GPL.

    pbrt is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.

 */


// shapes/heightfield.cpp*
#include "stdafx.h"
#include "shapes/heightfield.h"
#include "shapes/trianglemesh.h"
#include "paramset.h"

// Heightfield Method Definitions
Heightfield::Heightfield(const Transform *o2w, const Transform *w2o,
        bool ro, int x, int y, const float *zs)
    : Shape(o2w, w2o, ro) {
    nx = x;
    ny = y;
    z = new float[nx*ny];
    memcpy(z, zs, nx*ny*sizeof(float));
}


Heightfield::~Heightfield() {
    delete[] z;
}


BBox Heightfield::ObjectBound() const {
    float minz = z[0], maxz = z[0];
    for (int i = 1; i < nx*ny; ++i) {
        if (z[i] < minz) minz = z[i];
        if (z[i] > maxz) maxz = z[i];
    }
    return BBox(Point(0,0,minz), Point(1,1,maxz));
}


bool Heightfield::CanIntersect() const {
    return false;
}


void Heightfield::Refine(vector<Reference<Shape> > &refined) const {
    int ntris = 2*(nx-1)*(ny-1);
    refined.reserve(ntris);
    int *verts = new int[3*ntris];
    Point *P = new Point[nx*ny];
    float *uvs = new float[2*nx*ny];
    int nverts = nx*ny;
    int x, y;
    // Compute heightfield vertex positions
    int pos = 0;
    for (y = 0; y < ny; ++y) {
        for (x = 0; x < nx; ++x) {
            P[pos].x = uvs[2*pos]   = (float)x / (float)(nx-1);
            P[pos].y = uvs[2*pos+1] = (float)y / (float)(ny-1);
            P[pos].z = z[pos];
            ++pos;
        }
    }

    // Fill in heightfield vertex offset array
    int *vp = verts;
    for (y = 0; y < ny-1; ++y) {
        for (x = 0; x < nx-1; ++x) {
#define VERT(x,y) ((x)+(y)*nx)
            *vp++ = VERT(x, y);
            *vp++ = VERT(x+1, y);
            *vp++ = VERT(x+1, y+1);
    
            *vp++ = VERT(x, y);
            *vp++ = VERT(x+1, y+1);
            *vp++ = VERT(x, y+1);
        }
#undef VERT
    }
    ParamSet paramSet;
    paramSet.AddInt("indices", verts, 3*ntris);
    paramSet.AddFloat("uv", uvs, 2 * nverts);
    paramSet.AddPoint("P", P, nverts);
    refined.push_back(CreateTriangleMeshShape(ObjectToWorld, WorldToObject, ReverseOrientation, paramSet));
    delete[] P;
    delete[] uvs;
    delete[] verts;
}


Heightfield *CreateHeightfieldShape(const Transform *o2w, const Transform *w2o,
        bool reverseOrientation, const ParamSet &params) {
    int nu = params.FindOneInt("nu", -1);
    int nv = params.FindOneInt("nv", -1);
    int nitems;
    const float *Pz = params.FindFloat("Pz", &nitems);
    Assert(nitems == nu*nv);
    Assert(nu != -1 && nv != -1 && Pz != NULL);
    return new Heightfield(o2w, w2o, reverseOrientation, nu, nv, Pz);
}

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